1. Field of the Invention
The present invention relates to an image processing apparatus configured to control line width correction of an image to be printed, an image processing method, and a computer program thereof. For example, the present invention relates to an image processing apparatus configured to correct a line width of a thin line or a character which is printed, using a correction parameter, an image processing method, and an image processing program thereof.
2. Description of the Related Art
In recent years, an electrophotographic technique has been highly developed. A copying machine has a mounted printer engine having a printing density of 1200 dots per inch (dpi) or greater to enable high-quality printing. Consequently, reproducibility of a thin line of an image or a character has been more important. However, the reproducibility of a thin line or a character may be changed depending on a use environment or long-term use of the copying machine.
Then, conventionally, a correction technique (calibration) has been proposed, which maintains the line width of a thin line or a character to be printed, in a constant condition and maintains reproducibility. A method for reading a document on which a thin line is printed, using a scanner, to acquire a first image, and thereafter reading a printed product on which the first image is printed, using the scanner, to acquire a second image is discussed in Japanese Patent Application Laid-Open No. 2010-113070. A method for comparing the first image with the second image, to calculate a correction amount of a line width so that a line width of the first image is equal to that of the second image is discussed in Japanese Patent Application Laid-Open No. 2010-113070. A method for subjecting image data to be printed, using the correction amount to dot adding (or dot thinning) processing, to control line width correction is discussed in Japanese Patent Application Laid-Open No. 2010-113070.
When the image is read using the scanner, blurring (edge blurring) occurs in an edge portion of the thin line on the read image data under the influence of a light condition and deviation of a focus. The degree of the edge blurring is different depending on the line width of the thin line. The method discussed in Japanese Patent Application Laid-Open No. 2010-113070 compares the two images (the first image and the second image) having thin lines having different line widths such as the document and the printed product obtained by copying and printing the document, and corrects images. The method discussed in Japanese Patent Application Laid-Open No. 2010-113070 corrects images without considering different degrees of edge blurring of the read images. More specifically, when the method corrects images so that the line widths of both the images are equal to each other using the two read images in which the degrees of edge blurring are different and correct line widths are not known, it becomes difficult to precisely correct the line width.